A variety of methods are known in the art for preparing snack foods. However, most, if not all, of these methods rely on cooking or processing techniques which increase the caloric value of the basic foodstuff used as the starting material. Perhaps the best example of this increased calorie processing technique is fried potato chip products. The usual method of frying potato chip products involves the slicing of raw potatoes, the insertion of these slices into a reservoir of hot fat for a predetermined period of time so that the slices are fried to a crisp state, followed by the removal of the fried chips from the fat. The effect of frying on the potato slices is to reduce the water content of the slices while allowing oil uptake. This results in the appropriate surface color and crispness. Fresh potatoes contain approximately 85% moisture. The finished potato chip product contains from 30% to 45% oil or fat of the total weight of the potato chip and less than 5% moisture.
A high fat content is undesirable for a number of reasons. Obviously, the caloric value of the final product would be increased after processing. In addition, a low fat content chip cannot be made with deep fat frying processes and the fat content cannot be controlled since fat is absorbed throughout the frying operation. The deep fat frying process also shortens the shelf stability of the potato chip. Moreover, the frying process is difficult to control and often results in overly cooked potato chips.
The disadvantages associated with the use of the foregoing prior art process have been noted. A number of improvements have been designed to overcome these disadvantages. However, the preparation of a low calorie snack food product without the use of cooking oil or some other additive has not yet been achieved.
U.S. Pat. No. 3,576,647 discloses a process for preparing potato chips having a relatively uniform color, texture and shape. To achieve this degree of uniformity, thin pieces of edible dough are shaped to a predetermined surface conformation. The prepared dough is contained in mold halves and is then placed in contact with a frying medium. A fried product of relatively uniform color, texture and shape is obtained.
Microwave heating is a relatively new procedure used in the production of potato chips. U.S. Pat. No. 4,283,425 discloses a process for preparing low fat potato chips by coating a raw potato slice with globular protein and subjecting the raw coated slice to microwave heating. However, even though the use of a deep fat fryer has been eliminated, the use of an edible oil is still suggested.
In the prior art processes, the presence of oxygen and water vapor within the final package reacts with the frying fat retained by the chips. The fat becomes rancid and thereby imparts an undesirable rancid odor and taste to the chips. The water vapor causes the chips to lose crispness and become stale in flavor. As a result, the normal shelf life of potato chips and other snack food products is relatively short, being on the order of two or three weeks because of the onset of oxidation rancidity and staling. After this period, the chips are not in an acceptable condition and those not sold and consumed by that time are usually discarded. Thus, oil-free or fat-free potato chips are desirable.